Project Summary The primary goal of the proposed research is to advance the quality of care provided to people with lower limb amputation (LLA) by developing a state-of-the-art, dynamic measurement system that can be incorporated into clinical practices, research studies, and electronic health record systems. Performance-based measurement of important health outcomes, like prosthetic mobility, is widely acknowledged as an important element of professional practice and a primary contributor to positive patient outcomes. Standardized performance-based measures are well suited to measuring clinical patients, but they are inhibited by a structure that requires a patient to complete a large number of tasks, many of which provide limited value to the clinical assessment. Modern measurement methods, which have been successfully applied to enhancing the quality and efficiency of patient-reported measures, can be extended to address inefficiencies in performance-based testing. In this project, we apply advances in psychometric modelling and computer technology to create a dynamic measurement system that targets the capabilities of each individual patient. In Aim 1, we will develop a bank of tasks suited to measuring mobility of people with LLA in clinical settings. A large, diverse sample of 500 prosthetic limb users will be recruited in a national cross-sectional study to test candidate tasks. Results will be quantitatively analyzed using item response theory (IRT) to create a calibrated bank of performance tasks that can be targeted to patients with similar characteristics (eg, people with LLA due to diabetes) using fixed-length task sets, or targeted to individual patients using computerized adaptive testing (CAT). In Aim 2, we will conduct statistical simulations to maximize the efficiency of the CAT algorithm. We will use information from patient-report outcome measures to identify the first task and unique stopping rules to ensure patients with very high or very low mobility are not unnecessarily burdened. We will develop an application to allow clinicians and researchers to administer the measure, and software to facilitate integration into electronic health record systems. In Aim 3, we will evaluate the reliability, validity, and efficiency of the developed system for measuring mobility in people with LLA. A diverse sample of 100 prosthetic limb users will be recruited to participate in a repeated-measures study. We will compare results from the developed system to existing measures of mobility, balance, and physical function. Successful completion of this project will provide a valid, reliable, interpretable, and efficient tool for measuring mobility outcomes in people with LLA and a model for enhancing performance-based measurement in other clinical populations.